MEMS device and method of forming MEMS device

ABSTRACT

A method of forming a MEMS device includes providing a substructure including a base material and at least one conductive layer formed on a side of the base material, forming a dielectric layer over the at least one conductive layer of the substructure, defining an actuating area for the MEMS device on the dielectric layer, including depositing a conductive material on the dielectric layer and communicating the conductive material with the at least one conductive layer of the substructure through the dielectric layer, forming a sacrificial layer over the conductive material and the dielectric layer, including depositing silicon over the conductive material and the dielectric layer, and forming a substantially planar surface of the silicon, forming an actuating element over the sacrificial layer within the actuating area, including communicating the actuating element with the conductive material of the actuating area through the sacrificial layer, and substantially removing the sacrificial layer between the actuating element and the dielectric layer.

BACKGROUND

Microelectromechanical systems or MEMS devices include micromachinedsubstrates integrated with electronic microcircuits. Such devices mayform, for example, microsensors or microactuators which operate basedon, for example, electromagnetic, electrostrictive, thermoelectric,piezoelectric, or piezoresistive effects. MEMS devices have been formedon insulators or other substrates using micro-electronic techniques suchas photolithography, vapor deposition, and etching.

An example of a MEMS device includes a micro-mirror device. Themicro-mirror device can be operated as a light modulator for amplitudeand/or phase modulation of incident light. One application of amicro-mirror device is in a display system. As such, multiplemicro-mirror devices are arranged in an array such that eachmicro-mirror device provides one cell or pixel of the display. Aconventional micro-mirror device includes an electrostatically actuatedmirror supported for rotation about an axis of the mirror. As such,rotation of the mirror about the axis may be used to modulate incidentlight by directing the incident light in different directions.

Conventional techniques for forming a micro-mirror device includephotolithography, vapor deposition, and etching. Thus, to reduce cost ofthe micro-mirror device, it is desirable to minimize the number ofprocessing steps and/or reduce processing time. In addition, to minimizeprocessing limitations, such as processing temperatures, it is alsodesirable to increase the number of materials which are suitable for usewhile forming the micro-mirror device.

For these and other reasons, there is a need for the present invention.

SUMMARY

One aspect of the present invention provides a method of forming a MEMSdevice. The method includes providing a substructure including a basematerial and at least one conductive layer formed on a side of the basematerial, forming a dielectric layer over the at least one conductivelayer of the substructure, defining an actuating area for the MEMSdevice on the dielectric layer, including depositing a conductivematerial on the dielectric layer and communicating the conductivematerial with the at least one conductive layer of the substructurethrough the dielectric layer, forming a sacrificial layer over theconductive material and the dielectric layer, including depositingsilicon over the conductive material and the dielectric layer, andforming a substantially planar surface of the silicon, forming anactuating element over the sacrificial layer within the actuating area,including communicating the actuating element with the conductivematerial of the actuating area through the sacrificial layer, andsubstantially removing the sacrificial layer between the actuatingelement and the dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating one embodimentof a portion of a micro-mirror device according to the presentinvention.

FIG. 2 is a perspective view illustrating one embodiment of a portion ofa micro-mirror device according to the present invention.

FIGS. 3A-3G illustrate one embodiment of forming a micro-mirror deviceaccording to the present invention.

FIGS. 4A-4H illustrate another embodiment of forming a micro-mirrordevice according to the present invention.

FIG. 5 is a block diagram illustrating one embodiment of a displaysystem including a micro-mirror device according to the presentinvention.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

FIG. 1 illustrates one embodiment of a micro-mirror device 10.Micro-mirror device 10 is a micro-actuator which relies on electrical tomechanical conversion to generate a force and cause movement oractuation of a body or element. In one embodiment, as described below, aplurality of micro-mirror devices 10 are arranged to form an array ofmicro-mirror devices. As such, the array of micro-mirror devices may beused to form a display. As such, each micro-mirror device 10 constitutesa light modulator for modulation of incident light and provides one cellor pixel of the display. In addition, micro-mirror device 10 may also beused in other imaging systems such as projectors and may also be usedfor optical addressing.

In one embodiment, as described below, micro-mirror device 10 is formedwith a sacrificial silicon layer. As such, processing temperaturelimitations may be reduced since higher processing temperatures,compared to processing temperatures of other materials, can be usedwhile forming micro-mirror device 10. Thus, the number of materialswhich are suitable for use while forming micro-mirror device 10 may beincreased. In addition, in one embodiment, as described below, areflective element of micro-mirror device 10 includes a hinge materialand a reflective material formed on the hinge material such that thehinge material facilitates flexure or movement of the reflectiveelement.

In one embodiment, as illustrated in FIG. 1, micro-mirror device 10includes a substrate 20, a plate 30, and an actuating element 40.Preferably, plate 30 is oriented substantially parallel to a surface 22of substrate 20 and spaced from surface 22 so as to define a cavity 50therebetween. Actuating element 40 is interposed between surface 22 ofsubstrate 20 and plate 30. As such, actuating element 40 is positionedwithin cavity 50. In one embodiment, actuating element 40 is supportedrelative to substrate 20 by a support or post 24 extending from surface22 of substrate 20.

In one embodiment, actuating element 40 is actuated so as to movebetween a first position 47 and a second position 48 relative tosubstrate 20 and plate 30. Preferably, actuating element 40 moves ortilts at an angle about an axis of rotation. As such, first position 47of actuating element 40 is illustrated as being substantially horizontaland substantially parallel to substrate 20 and second position 48 ofactuating element 40 is illustrated as being oriented at an angle tofirst position 47. Movement or actuation of actuating element 40relative to substrate 20 and plate 30 is described in detail below.

Preferably, plate 30 is a transparent plate 32 and actuating element 40is a reflective element 42. In one embodiment, transparent plate 32 is aglass plate. Other suitable planar translucent or transparent materials,however, may be used. Examples of such a material include quartz andplastic.

Reflective element 42 includes a reflective surface 44. In oneembodiment, reflective element 42 is formed of a uniform material havinga suitable reflectivity to form reflective surface 44. Examples of sucha material include polysilicon or a metal such as aluminum. In anotherembodiment, reflective element 42 is formed of a base material such aspolysilicon with a reflective material such as aluminum or silverdisposed on one or more sides of the base material. In addition,reflective element 42 may be formed of a non-conductive material or maybe formed of or include a conductive material.

As illustrated in the embodiment of FIG. 1, micro-mirror device 10modulates light generated by a light source (not shown) located on aside of transparent plate 32 opposite of substrate 20. The light sourcemay include, for example, ambient and/or artificial light. As such,input light 12, incident on transparent plate 32, passes throughtransparent plate 32 into cavity 50 and is reflected by reflectivesurface 44 of reflective element 42 as output light 14. Thus, outputlight 14 passes out of cavity 50 and back through transparent plate 32.

The direction of output light 14 is determined or controlled by theposition of reflective element 42. For example, with reflective element42 in first position 47, output light 14 is directed in a firstdirection 14 a. However, with reflective element 42 in second position48, output light 14 is directed in a second direction 14 b. Thus,micro-mirror device 10 modulates or varies the direction of output light14 generated by input light 12. As such, reflective element 42 can beused to steer light into, and/or away from, an optical imaging system.

In one embodiment, first position 47 is a neutral position of reflectiveelement 42 and represents an “ON” state of micro-mirror device 10 inthat light is reflected, for example, to a viewer or onto a displayscreen, as described below. Thus, second position 48 is an actuatedposition of reflective element 42 and represents an “OFF” state ofmicro-mirror device 10 in that light is not reflected, for example, to aviewer or onto a display screen.

In one embodiment, reflective element 42 is moved between first position47 and second position 48 by applying an electrical signal to anelectrode 60 formed on substrate 20. In one embodiment, electrode 60 isformed on surface 22 of substrate 20 adjacent an end or edge ofreflective element 42. Application of an electrical signal to electrode60 generates an electric field between electrode 60 and reflectiveelement 42 which causes movement of reflective element 42 between firstposition 47 and second position 48. Preferably, when the electricalsignal is removed from electrode 60, reflective element 42 persists orholds second position 48 for some length of time. Thereafter, restoringforces of reflective element 42 pull or return reflective element 42 tofirst position 47.

In one embodiment, a conductive via 26 is formed in and extends throughpost 24. Conductive via 26 is electrically coupled to reflective element42 and, more specifically, conductive material of reflective element 42.As such, reflective element 42 is moved between first position 47 andsecond position 48 by applying an electrical signal to electrode 60 andreflective element 42. More specifically, electrode 60 is energized toone polarity and the conductive material of reflective element 42 isenergized to an opposite polarity. Thus, application of an electricalsignal of one polarity to electrode 60 and an electrical signal of anopposite polarity to reflective element 42 generates an electric fieldbetween electrode 60 and reflective element 42 which causes movement ofreflective element 42 between first position 47 and second position 48.

In another embodiment, reflective element 42 is moved between firstposition 47 and second position 48 by applying an electrical signal toreflective element 42. More specifically, the electrical signal isapplied to conductive material of reflective element 42 by way ofconductive via 26 through post 24. As such, application of an electricalsignal to reflective element 42 generates an electric field which causesmovement of reflective element 42 between first position 47 and secondposition 48.

Additional embodiments of actuation of micro-mirror device 10 aredescribed, for example, in U.S. patent application Ser. No. 10/136,719,filed on Apr. 30, 2002, entitled “Micro-Mirror Device”, assigned to theassignee of the present invention and incorporated herein by reference.

FIG. 2 illustrates one embodiment of reflective element 42. Reflectiveelement 42 has a reflective surface 44 and includes a substantiallyrectangular-shaped outer portion 80 and a substantiallyrectangular-shaped inner portion 84. In one embodiment, reflectivesurface 44 is formed on both outer portion 80 and inner portion 84.Outer portion 80 has four contiguous side portions 81 arranged to form asubstantially rectangular-shaped opening 82. As such, inner portion 84is positioned within opening 82. Preferably, inner portion 84 ispositioned symmetrically within opening 82.

In one embodiment, a pair of hinges 86 extend between inner portion 84and outer portion 80. Hinges 86 extend from opposite sides or edges ofinner portion 84 to adjacent opposite sides or edges of outer portion80. Preferably, outer portion 80 is supported by hinges 86 along an axisof symmetry. More specifically, outer portion 80 is supported about anaxis that extends through the middle of opposed edges thereof. As such,hinges 86 facilitate movement of reflective element 42 between firstposition 47 and second position 48, as described above (FIG. 1). Morespecifically, hinges 86 facilitate movement of outer portion 80 betweenfirst position 47 and second position 48 relative to inner portion 84.

In one embodiment, hinges 86 include torsional members 88 havinglongitudinal axes 89 oriented substantially parallel to reflectivesurface 44. Longitudinal axes 89 are collinear and coincide with an axisof symmetry of reflective element 42. As such, torsional members 88twist or turn about longitudinal axes 89 to accommodate movement ofouter portion 80 between first position 47 and second position 48relative to inner portion 84.

In one embodiment, reflective element 42 is supported relative tosubstrate 20 by support or post 24 extending from surface 22 ofsubstrate 20. More specifically, post 24 supports inner portion 84 ofreflective element 42, and outer portion 80 of reflective element 42 issupported by hinges 86 extending from inner portion 84. In oneembodiment, post 24 is formed by conductive via 26 extending throughinner portion 84 to a conductive layer of substrate 20.

FIGS. 3A-3G illustrate one embodiment of forming micro-mirror device 10.In one embodiment, as illustrated in FIG. 3A, micro-mirror device 10 isformed on a substructure 200. In one embodiment, substructure 200includes a complementary metal oxide semi-conductor (CMOS) structure. Assuch, substructure 200 includes a base material 210 and at least oneconductive layer 220 formed on a first side 212 of base material 210.Conductive layer 220 includes, for example, titanium (Ti), titaniumnitride (TiN), copper (Cu), gold (Au), and/or aluminum (Al). Conductivelayer 220 is formed, for example, by deposition, and patterned byphotolithography and etching.

In one embodiment, substructure 200 includes a dielectric layer 214formed on first side 212 of base material 210. As such, conductive layer220 of substructure 200 is formed over dielectric layer 214. Dielectriclayer 214 includes, for example, a silicon oxide such astetraethylorthosilicate (TEOS). In one embodiment, deposited layers ofsubstructure 200 including, for example, dielectric layer 214 areplanarized during formation of substructure 200 to create asubstantially planar substrate for micro-mirror device 10.

In one embodiment, conductive material of conductive layer 220 forms anelectrical contact area 202 of substructure 200 and an actuating area204 of substructure 200. Electrical contact area 202 defines an areawhere electrical connection to micro-mirror device 10 is to be made, andactuating area 204 defines an area where actuating element 40 ofmicro-mirror device 10 is to be formed, as described below. As such,conductive layer 220 of substructure 200 constitutes an interconnectlevel of the CMOS circuit.

As illustrated in the embodiment of FIG. 3A, to form micro-mirror device10 on substructure 200, a dielectric layer 222 is formed over conductivelayer 220 of substructure 200. As such, dielectric layer 222 formssurface 22 of substrate 20, as described above. In one embodiment,dielectric layer 222 is formed by depositing a dielectric material overconductive layer 220. The dielectric material includes, for example,TEOS or other form of silicon oxide. In one embodiment, the dielectricmaterial of dielectric layer 222 is planarized to create a substantiallyplanar surface on which electrodes 60 are formed, as described below.

After dielectric layer 222 is formed over conductive layer 220, aconductive material 224 is deposited and patterned on dielectric layer222. In one embodiment, conductive material 224 is deposited andpatterned by photolithography and etching within actuating area 204 ofsubstructure 200. As such, conductive material 224 defines electrode 60on dielectric layer 222. In one embodiment, conductive material 224includes aluminum or an aluminum alloy such as an aluminum siliconalloy.

In one embodiment, conductive material 224 communicates with conductivelayer 220 of substructure 200 by a conductive via 226 formed throughdielectric layer 222. It is understood that FIG. 3A is a schematicrepresentation of substructure 200 and that the actual configuration ofconductive layers and conductive vias formed between conductive layersmay be more complicated than that illustrated.

In one embodiment, as illustrated in FIG. 3A, conductive material ofconductive layer 220 is patterned to form an electrical contact pad 221for micro-mirror device 10. Electrical contact pad 221 is formed, forexample, in electrical contact area 202 of substructure 200. As such, anopening 223 is formed through dielectric layer 222 to electrical contactpad 221. Thus, electrical contact pad 221 provides a point forelectrical connection for micro-mirror device 10.

As illustrated in the embodiment of FIG. 3B, to form actuating element40, a sacrificial layer 230 is formed over conductive material 224 anddielectric layer 222, including within opening 223. In one embodiment,sacrificial layer 230 is formed by depositing a sacrificial materialover conductive material 224 and dielectric layer 222. The materialforming sacrificial layer 230 is deposited, for example, by chemicalvapor deposition (CVD) or plasma enhanced CVD (PECVD). In oneembodiment, the material forming sacrificial layer 230 includes, forexample, silicon.

Sacrificial layer 230 is sacrificial in that the material formingsacrificial layer 230 is substantially removed during subsequentprocessing while forming actuating element 40, as described below. Byforming sacrificial layer 230 of silicon, for example, processtemperature limitations are reduced since higher processingtemperatures, compared to processing temperatures of other materials,can be used during processing of micro-mirror device 10.

After the material of sacrificial layer 230 is deposited over conductivematerial 224 and dielectric layer 222, the material is planarized tocreate a substantially flat or planar surface 232 of sacrificial layer230. In one embodiment, the material of sacrificial layer 230 isplanarized by a chemical mechanical polishing (CMP) process.

Next, as illustrated in the embodiment of FIG. 3C, a mask layer 240 isformed over sacrificial layer 230. In one embodiment, mask layer 240 isformed by deposition and patterned, for example, by photolithography oretching to expose an area of sacrificial layer 230 and define where anopening 234 is to be formed through sacrificial layer 230 to conductivematerial 224.

In one embodiment, opening 234 through sacrificial layer 230 is formedby chemical etching. Thus, mask layer 240 is formed of a material whichis resistant to the etchant used for etching opening 234. Examples of amaterial suitable for mask layer 240 include a hard mask material suchas silicon dioxide or silicon nitride, or a photoimageable material suchas photoresist. After opening 234 is formed, mask layer 240 is strippedor removed.

As illustrated in the embodiments of FIGS. 3D-3G, after opening 234 isformed through sacrificial layer 230 and mask layer 240 is removed,actuating element 40 is formed. In one embodiment, actuating element 40includes reflective element 42 of micro-mirror device 10. Reflectiveelement 42 is formed, for example, by depositing one or more layers ofone or more materials over sacrificial layer 230, and patterning thematerials to define reflective element 42. The materials are deposited,for example, by physical vapor deposition (PVD), CVD, or PECVD, andpatterned, for example, by photolithography and etching.

As illustrated in the embodiment of FIG. 3D, reflective element 42 isformed by depositing a first material 250 over sacrificial layer 230 andwithin opening 234 of sacrificial layer 230. In one embodiment, material250 which is deposited within opening 234 forms a conductive via 251through sacrificial layer 230 to conductive material 224. As such,conductive via 251 forms post 24 and conductive via 26 of micro-mirrordevice 10, as described above and illustrated in FIG. 1. Thus, material250 includes a conductive material. In one embodiment, for example,material 250 includes aluminum or an aluminum alloy such as an aluminumsilicon alloy. In addition, in one embodiment, material 250 constitutesa hinge material of reflective element 42 and forms hinges 86 (FIG. 2)of micro-mirror device 10, as described below.

In one embodiment, as illustrated in FIG. 3D, after material 250 isdeposited over sacrificial layer 230, a protective material 252 isdeposited and patterned on material 250. In one embodiment, protectivematerial 252 is deposited by deposition and patterned byphotolithography and etching to define where hinges 86 (FIG. 2) ofmicro-mirror device 10 are to be formed. More specifically, protectivematerial 252 is patterned to protect areas of material 250 which formhinges 86, as described below. In one embodiment, protective material252 includes TEOS or other form of silicon oxide.

Next, as illustrated in the embodiment of FIG. 3E, reflective element 42is further formed by depositing a second material 254 over protectivematerial 252 and material 250. In one embodiment, material 254constitutes reflective material of reflective element 42 and formsreflective surface 44 of reflective element 42. Thus, material 254includes a reflective material. In one embodiment, for example, material254 includes aluminum or an aluminum alloy such as an aluminum siliconalloy.

In one embodiment, as illustrated in FIG. 3E, after material 254 isdeposited over protective material 252 and material 250, a mask layer260 is formed over material 254. In one embodiment, mask layer 260 isformed by deposition and patterned, for example, by photolithography oretching to form openings 262 in mask layer 260 and expose areas ofmaterial 254. As such, the exposed areas of material 254 include areaswhich define where material 254 and protective material 252 are to beremoved to form hinges 86 (FIG. 2) of reflective element 42. In oneembodiment, a dimension D1 of openings 262 is less than a dimension D2of protective material 252. As such, protective material 252 protectsmaterial 250 during forming of hinges 86, as described below.

As illustrated in the embodiment of FIG. 3F, hinges 86 are formed byforming openings 256 through material 254 and protective material 252 tomaterial 250. In one embodiment, openings 256 are formed by chemicaletching through openings 262 of mask layer 260. As such, protectivematerial 252 protects and/or controls etching into material 250. Afteropenings 256 are formed, mask layer 260 is stripped or removed.

Next, as illustrated in the embodiment of FIG. 3G, sacrificial layer 230is substantially removed. As such, the material of sacrificial layer 230is removed from between reflective element 42 and conductive material224 and dielectric layer 222. Thus, reflective element 42, includingreflective surface 44 and hinges 86, is released and conductive material224, including electrode 60, is exposed. In addition, electrical contactpad 221 of electrical contact area 202 is exposed.

In one embodiment, sacrificial layer 230 is removed by a chemical etchprocess. As such, conductive material 224, dielectric layer 222,conductive layer 220, and the materials of reflective element 42 areeach selected so as to be resistant to the particular etchant used forremoving sacrificial layer 230. In one embodiment, the etch process forremoving sacrificial layer 230 is a dry etch, such as a plasma-basedfluorinated etch using, for example, SF₆, CF₄, C₂F₆, or a combination ofgases.

FIGS. 4A-4H illustrate another embodiment of forming micro-mirror device10. As described above, substructure 200 of micro-mirror device 10includes base material 210, dielectric layer 214, and conductive layer220. In addition, dielectric layer 222 is formed over conductive layer220 and conductive material 224 is deposited on dielectric layer 222 toform electrode 60.

In one embodiment, as illustrated in FIG. 4A, before sacrificial layer230 is formed, a barrier layer 270 is formed over conductive material224 and dielectric layer 222. Barrier layer 270 is provided to preventthe diffusion of conductive material 224 and/or the material ofdielectric layer 222 with the material of sacrificial layer 230 duringsubsequent processing of micro-mirror device 10, as described below. Inone embodiment, material suitable for barrier layer 270 includes, forexample, titanium nitride, silicon nitride, or silicon oxide.

As illustrated in the embodiment of FIG. 4B, after barrier layer 270 isformed, sacrificial layer 230 is formed over barrier layer 270. In oneembodiment, sacrificial layer 230 is formed by depositing a sacrificialmaterial over barrier layer 270. As described above, the materialforming sacrificial layer 230 is deposited, for example, by CVD orPECVD. In one embodiment, the material forming sacrificial layer 230includes, for example, silicon. After the material of sacrificial layer230 is deposited over barrier layer 270, the material is planarized tocreate substantially flat surface 232 of sacrificial layer 230, asdescribed above.

In one embodiment, as illustrated in FIG. 4B, after sacrificial layer230 is planarized, another barrier layer 272 is formed over sacrificiallayer 230. Barrier layer 272 is provided to prevent the diffusion of thematerial of sacrificial layer 230 with the materials of reflectiveelement 42 during subsequent processing of micro-mirror device 10, asdescribed below. In one embodiment, material suitable for barrier layer272 includes, for example, titanium nitride, silicon nitride, or siliconoxide.

Next, as illustrated in the embodiment of FIG. 4C, mask layer 240 isformed over barrier layer 272. In one embodiment, as described above,mask layer 240 is formed by deposition and patterned, for example, byphotolithography to expose an area where opening 234 is to be formedthrough barrier layer 272, sacrificial layer 230, and barrier layer 270to conductive material 224. Opening 234 is formed, for example, bychemical etching, as described above. After opening 234 is formed, masklayer 240 is stripped or removed.

As illustrated in the embodiments of FIGS. 4D-4H, after opening 234 isformed through barrier layer 272, sacrificial layer 230, and barrierlayer 270, and after mask layer 240 is removed, actuating element 40 isformed. In one embodiment, as described above, actuating element 40includes reflective element 42 of micro-mirror device 10.

As illustrated in the embodiment of FIG. 4D, reflective element 42 isformed by depositing first material 250 over barrier layer 272 andwithin opening 234. In one embodiment, as described above, materialdeposited within opening 234 forms conductive via 251 which representspost 24 and conductive via 26 of micro-mirror device 10. In addition,material 250 represents hinge material of reflective element 42 andforms hinges 86 (FIG. 2) of micro-mirror device 10. In one embodiment,material 250 includes aluminum, as described above. Also, as illustratedin the embodiment of FIG. 4D, after material 250 is deposited oversacrificial layer 230, protective material 252 is deposited andpatterned on material 250.

Next, as illustrated in the embodiment of FIG. 4E, reflective element 42is further formed by depositing a second material 254 over protectivematerial 252 and material 250. As described above, material 254represents reflective material of reflective element 42 and formsreflective surface 44 of reflective element 42. In one embodiment,material 254 includes aluminum, as described above. Also, as illustratedin the embodiment of FIG. 4E, after material 254 is deposited overprotective material 252 and material 250, mask layer 260 with openings262 is formed over material 254.

As illustrated in the embodiment of FIG. 4F, hinges 86 are formed byforming openings 256 through material 254 and protective material 252 tomaterial 250. In one embodiment, as described above, openings 256 areformed by chemical etching through openings 262 of mask layer 260. Afteropenings 256 are formed, mask layer 260 is stripped or removed.

In one embodiment, as illustrated in FIG. 4G, opening 223 throughdielectric layer 222 to electrical contact pad 221 is formed afterreflective element 42 is formed. As such, a mask layer 280 is formedover reflective element 42 and patterned to define where opening 223 isto be formed through sacrificial layer 230 and dielectric layer 222. Inone embodiment, opening 223 is formed by a chemical etch process. Afteropening 223 is formed, mask layer 280 is stripped or removed.

Next, as illustrated in the embodiment of FIG. 4H, sacrificial layer 230is substantially removed. In addition, barrier layers 270 and 272 arealso substantially removed. As such, reflective element 42, includingreflective surface 44 and hinges 86, is released and conductive material224, including electrode 60, is exposed. In one embodiment, sacrificiallayer 230, including barrier layers 270 and 272, are removed by achemical etch process. In one embodiment, as described above, the etchprocess includes a dry etch, such as a plasma-based fluorinated etchusing, for example, SF₆, CF₄, C₂F₆, or a combination of gases.

While the above description refers to the formation of a micro-mirrordevice, it is understand that the above processes are also applicable tothe formation of other MEMS devices, including multi-layer MEMS devices.In addition, it is understood that FIGS. 3A-3G and FIGS. 4A-4H are eachschematic illustrations of one embodiment of forming a micro-mirrordevice according to the present invention and that the actualconfiguration of layers and vias of the micro-mirror device may be morecomplicated than that illustrated.

In one embodiment, as illustrated in FIG. 5, micro-mirror device 10 isincorporated in a display system 500. Display system 500 includes alight source 510, source optics 512, a light processor or controller514, and projection optics 516. Light processor 514 includes multiplemicro-mirror devices 10 arranged in an array such that each micro-mirrordevice 10 constitutes one cell or pixel of the display.

In one embodiment, light processor 514 receives image data 518representing an image to be displayed. As such, light processor 514controls the actuation of micro-mirror devices 10 and the modulation oflight received from light source 510 based on image data 518. Themodulated light is then projected to a viewer or onto a display screen520.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A method of forming a micro-mirror device, the method comprising:providing a substructure including a base material and at least oneconductive layer formed on a side of the base material; forming a layerof dielectric material over the at least one conductive layer of thesubstructure; depositing a conductive material on the layer ofdielectric material, including communicating the conductive materialwith the at least one conductive layer of the substructure through thelayer of dielectric material; forming a sacrificial layer of siliconover the conductive material and the layer of dielectric material;forming a reflective element over the sacrificial layer of silicon; andsubstantially removing the sacrificial layer of silicon between thereflective element and the layer of dielectric material.
 2. The methodof claim 1, wherein depositing the conductive material includes formingat least one electrode on the layer of dielectric material, wherein thereflective element is adapted to move in response to application of anelectrical signal to the at least one electrode.
 3. The method of claim1, wherein forming the reflective element includes depositing a hingematerial over the sacrificial layer of silicon, depositing andpatterning a protective material over the hinge material, and depositinga reflective material over the protective material and the hingematerial, and includes removing a portion of the reflective material andthe protective material to expose a portion of the hinge material. 4.The method of claim 3, wherein the conductive material and at least thehinge material each include one of aluminum and an aluminum siliconalloy.
 5. The method of claim 1, wherein substantially removing thesacrificial layer includes dry etching the sacrificial layer.
 6. Themethod of claim 1, further comprising: forming a first layer of barriermaterial over the conductive material and the layer of dielectricmaterial, wherein forming the sacrificial layer includes forming thesacrificial layer over the first layer of barrier material, and whereinsubstantially removing the sacrificial layer includes substantiallyremoving the sacrificial layer and the first layer of barrier materialbetween the reflective element and the layer of dielectric material. 7.The method of claim 6, wherein the barrier material includes one oftitanium nitride, silicon nitride, and silicon oxide.
 8. The method ofclaim 6, further comprising: forming a second layer of barrier materialover the sacrificial layer of silicon, wherein forming the reflectiveelement includes forming the reflective element over the second layer ofbarrier material, and wherein substantially removing the sacrificiallayer includes substantially removing the second layer of barriermaterial, the sacrificial layer, and the first layer of barrier materialbetween the reflective element and the layer of dielectric material. 9.The method of claim 8, wherein the barrier material includes one oftitanium nitride, silicon nitride, and silicon oxide.
 10. The method ofclaim 1, further comprising: defining an electrical contact area for themicro-mirror device, including forming an opening through the dielectriclayer to the at least one conductive layer of the substructure.
 11. Themethod of claim 1, wherein the substructure includes a complementarymetal oxide semi-conductor structure.
 12. The method of claim 1, whereinthe base material of the substructure includes silicon and the at leastone conductive layer of the substructure includes aluminum.
 13. Themethod of claim 1, wherein the dielectric material includes siliconoxide.
 14. A micro-mirror device, comprising: a substructure including abase material and at least one conductive layer formed on a side of thebase material; a dielectric layer formed over the at least oneconductive layer of the substructure; at least one electrode formed onthe dielectric layer; and a reflective element extended over thedielectric layer and the at least one electrode, the reflective elementincluding a hinge material and a reflective material formed on the hingematerial, wherein the reflective element is adapted to move in responseto application of an electrical signal to the at least one electrode.15. The device of claim 14, wherein the hinge material of the reflectiveelement is adapted to flex to move the reflective element.
 16. Thedevice of claim 14, further comprising: an electrical contact areaincluding an opening formed through the dielectric layer to the at leastone conductive layer of the substructure.
 17. The device of claim 14,further comprising: a sacrificial layer of silicon formed over thedielectric layer and the at least one electrode, wherein the reflectiveelement is formed over the sacrificial layer, and wherein thesacrificial layer is adapted to be removed by an etch process after thereflective element is formed.
 18. The device of claim 17, wherein theetch process includes a dry etch process.
 19. The device of claim 17,further comprising: a first barrier layer formed over the dielectriclayer and the at least one electrode, wherein the sacrificial layer isformed over the first barrier layer, and wherein the sacrificial layerand the first barrier layer are adapted to be removed by the etchprocess after the reflective element is formed.
 20. The device of claim19, wherein the first barrier layer includes one of titanium nitride,silicon nitride, and silicon oxide.
 21. The device of claim 19, furthercomprising: a second barrier layer formed over the sacrificial layer ofsilicon, wherein the reflective element is formed over the secondbarrier layer, and wherein the second barrier layer, the sacrificiallayer, and the first barrier layer are adapted to be removed by the etchprocess after the reflective element is formed.
 22. The device of claim21, wherein the first barrier layer and the second barrier layer eachinclude one of titanium nitride, silicon nitride, and silicon oxide. 23.The device of claim 14, wherein the substructure includes acomplementary metal oxide semi-conductor structure.
 24. The device ofclaim 14, wherein the base material of the substructure includes siliconand the at least one conductive layer of the substructure includesaluminum.
 25. The device of claim 14, wherein the dielectric layerincludes silicon oxide.
 26. A display device including the micro-mirrordevice of claim
 14. 27. A micro-mirror device, comprising: asubstructure including a base material and at least one conductive layerformed on a side of the base material; a dielectric layer formed overthe at least one conductive layer of the substructure; at least oneelectrode formed on the dielectric layer; and a reflective elementextended over the dielectric layer and the at least one electrode,including means formed in the reflective element for facilitatingmovement of the reflective element in response to application of anelectrical signal to the at least one electrode.
 28. The device of claim27, wherein means formed in the reflective element for facilitatingmovement of the reflective element includes a hinge material and areflective material formed on the hinge material, wherein the hingematerial is adapted to flex to facilitate movement of the reflectiveelement.
 29. The device of claim 27, further comprising: means forforming the reflective element over the dielectric layer and the atleast one electrode, including a sacrificial layer of silicon formedover the dielectric layer and the at least one electrode, wherein thereflective element is formed over the sacrificial layer, and thesacrificial layer is removed after the reflective element is formed. 30.The device of claim 29, further comprising: means for protecting thedielectric layer and the at least one electrode from the sacrificiallayer of silicon; and means for protecting the reflective element fromthe sacrificial layer of silicon.
 31. The device of claim 30, whereinmeans for protecting the dielectric layer and the at least one electrodeincludes a first barrier layer formed over the dielectric layer and theat least one electrode, and wherein means for protecting the reflectiveelement includes a second barrier layer formed over the sacrificiallayer of silicon, wherein the sacrificial layer is formed over the firstbarrier layer, and the reflective element is formed over the secondbarrier layer, and wherein the second barrier layer, the sacrificiallayer of silicon, and the first barrier layer are removed after thereflective element is formed.